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Re: [dxwg] Use Case: Negotiation by Coordinate Reference System

From: Lars G. Svensson via GitHub <sysbot+gh@w3.org>
Date: Thu, 09 Aug 2018 12:02:11 +0000
To: public-dxwg-wg@w3.org
Message-ID: <issue_comment.created-411733697-1533816130-sysbot+gh@w3.org>
And finally a general comment: Yes, it might be that geospatial data has too many dimensions so that it's not possible to put all of it into a single profile, since a profile can only cater for a single value in each dimension (e. g. `crs=CRS84 and scale=1:100,000` or `crs=CRS84 and scale=1:50,000`) -- CRS and scale being orthogonal -- whereas it might be more convenient to have different Accept-headers for those two dimensions.
The main thinking (at least my main thinking) behind profiles is that we need something to convey additional constraints and semantics beyond what media types already offer and that profiles are orthogonal to media types. Another idea is that it's possible to create profiles that are unions of other profiles and that might be an approach to the geospatial use cases.
If we say that `urn:example:1` is a profile that says "Coordinates are in CRS84",`urn:example:2` is another profile that says "scale 1:50,000" and `urn:example:3" says "scale 1:100,000". Then we could create `urn:example:4' as the combination of `urn:example:1`and `urn:example:2` (i. e. CRS84 and 1;50,000).
The use of such a mechanism (composite profiles) is heavily discussed (#212, #216 and #217 come to mind). Comments on the usefulness of such an approach are most welcome.

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